.Dd February 23, 2020
.Dt EDITLINE 3
.Os
.Sh NAME
.Nm editline
.Nd command-line editing library with history
.Sh LIBRARY
.Lb libeditline
.Sh SYNOPSIS
.In editline.h
.Ft char *
.Fo readline
.Fa const char *prompt
.Fc
.Ft void
.Fo add_history
.Fa const char *line
.Fc
.Ft int
.Fo read_history
.Fa const char *filename
.Fc
.Ft int
.Fo write_history
.Fa const char *filename
.Fc
.Sh DESCRIPTION
.Nm
is a library that provides n line-editing interface with history.  It
is intended to be functionally equivalent with the
.Nm readline
library provided by the Free Software Foundation, but much smaller.  The
bulk of this manual page describes the basic user interface.  More APIs,
both native and for
.Nm readline
compatibility ,
are also available.  See the
.Cm editline.h
header file for details.
.Pp
The
.Fn readline
function displays the given
.Fa prompt
on stdout, waits for user input on stdin and then returns a line of text
with the trailing newline removed.  The data is returned in a buffer
allocated with
.Xr malloc 3 ,
so the space should be released with
.Xr free 3
when the calling program is done with it.
.Pp
Each line returned is automatically saved in the internal history list,
unless it happens to be equal to the previous line.  This is
configurable if you are building editline from source, i.e. if you would
rather like to call
.Fn add_history
manually.
.Pp
The
.Fn read_history
and
.Fn write_history
functions can be used to load and store the history of your application.
.Em Note:
these APIs do not do any tilde or environment variable expansion of the
given filename.
.Ss User Interface
A program that uses this library provides a simple emacs-like editing
interface to its users.  A line may be edited before it is sent to the
calling program by typing either control characters or escape sequences.
A control character, shown as a caret followed by a letter, is typed by
holding down the control key while the letter is typed.  For example,
.Cm ^A
is a control-A.  An escape sequence is entered by typing the escape key
followed by one or more characters.  The escape key is abbreviated as
.Cm ESC .
Note that unlike control keys, case matters in escape sequences;
.Cm ESC F
is not the same as
.Cm ESC f .
.Pp
An editing command may be typed anywhere on the line, not just at the
beginning.  In addition, a return may also be typed anywhere on the
line, not just at the end.
.Pp
Most editing commands may be given a repeat count,
.Ar n ,
where
.Ar n
is a number.  To enter a repeat count, type the escape key, the number,
and then the command to execute.  For example,
.Cm ESC 4 ^f
moves forward four characters.  If a command may be given a repeat count
then the text
.Cm [n]
is given at the end of its description.
.Pp
The following control characters are accepted:
.Pp
.Bl -tag -width "ESC DEL " -compact
.It ^A
Move to the beginning of the line
.It ^B
Move left (backwards) [n]
.It ^D
Delete character [n]
.It ^E
Move to end of line
.It ^F
Move right (forwards) [n]
.It ^G
Ring the bell
.It ^H
Delete character before cursor (backspace key) [n]
.It ^I
Complete filename (tab key); see below
.It ^J
Done with line (return key)
.It ^K
Kill to end of line (or column [n])
.It ^L
Redisplay line
.It ^M
Done with line (alternate return key)
.It ^N
Get next line from history [n]
.It ^P
Get previous line from history [n]
.It ^R
Search backward (forward if [n]) through history for text; prefixing the
string with a caret (^) forces it to match only at the beginning of a
history line
.It ^T
Transpose characters
.It ^V
Insert next character, even if it is an edit command
.It ^W
Wipe to the mark
.It ^X^X
Exchange current location and mark
.It ^Y
Yank back last killed text
.It ^[
Start an escape sequence (escape key)
.It ^]c
Move forward to next character
.Cm c
.It ^?
Delete character before cursor (delete key) [n]
.El
.Pp
The following escape sequences are provided:
.Pp
.Bl -tag -width "ESC DEL " -compact
.It ESC ^H
Delete previous word (backspace key) [n]
.It ESC DEL
Delete previous word (delete key) [n]
.It ESC SP
Set the mark (space key); see ^X^X and ^Y above
.It ESC\ .
Get the last (or [n]'th) word from previous line
.It ESC\ ?
Show possible completions; see below
.It ESC <
Move to start of history
.It ESC >
Move to end of history
.It ESC b
Move backward a word [n]
.It ESC d
Delete word under cursor [n]
.It ESC f
Move forward a word [n]
.It ESC l
Make word lowercase [n]
.It ESC m
Toggle if 8bit chars display normally or with an
.Ar M-
prefix
.It ESC u
Make word uppercase [n]
.It ESC y
Yank back last killed text
.It ESC v
Show library version
.It ESC w
Make area up to mark yankable
.It ESC nn
Set repeat count to the number nn
.It ESC C
Read from environment variable
.Ar $C ,
where
.Ar C
is an uppercase letter
.El
.Pp
The
.Nm
library has a small macro facility.  If you type the escape key followed
by an uppercase letter,
.Ar C ,
then the contents of the environment variable
.Ar $C
are read in as if you had typed them at the keyboard.  For example, if
the variable
.Ar $L
contains the following:
.Pp
.Dl ^A^Kecho '^V^[[H^V^[[2J'^M
.Pp
Then typing
.Cm ESC L
will move to the beginning of the line, kill the entire line, enter the
echo command needed to clear the terminal (if your terminal is like a
VT-100), and send the line back to the shell.
.Pp
The
.Nm
library also does filename completion.  Suppose the root directory has
the following files in it:
.Pp
.Dl bin	vmunix
.Dl core	vmunix.old
.Pp
If you type
.Cm rm /v
and then the tab key,
.Nm
will then finish off as much of the name as possible by adding
.Ar munix .
Because the name is not unique, it will then beep.  If you type the
escape key and a question mark, it will display the two choices.  If you
then type a period and a tab, the library will finish off the filename
for you:
.Pp
.Bd -ragged -offset indent
rm /v[TAB]
.Em munix
\&.[TAB]
.Em old
.Ed
.Pp
The tab key is shown by [TAB] and the automatically-entered text
is shown in italics, or underline.
.Sh USAGE
To include
.Nm
in your program, call it as you do any other function and link your
program with
.Ar -leditline .
.Ss Example
The following brief example lets you enter a line and edit it, then displays it.
.Pp
.Bd -literal -offset indent
#include <stdio.h>
#include <stdlib.h>
#include <editline.h>

int main(void)
{
	char *p;

	while ((p = readline("CLI> "))) {
	        puts(p);
	        free(p);
	}

	return 0;
}
.El
.Sh AUTHORS
The original editline library was posted to comp.sources.unix newsgroup
by created by Simmule R. Turner and Rich Salz in 1992.  It now exists in
several forks: Debian, Minix, Heimdal, Festival speech tools, Mozilla,
Google Gadgets for Linux, and many others.  The original manual page was
made by David W. Sanderson.
.Pp
This version stems from the Minix 2 sources, but has since evolved to
include patches from all relevant forks.  It is currently maintained by
.An Joachim Wiberg
at
.Lk https://github.com/troglobit/editline "GitHub" .
.Sh BUGS
Does not handle multiple lines or unicode characters well.
